A central air conditioner, particularly serving as a current centrifugal water chilling unit having a maximum refrigeration capacity, generates higher noises inevitably in a running process. These noises seriously pollute a surrounding environment, and bring a great harm to device users and maintainers. People, frequently located in the high-decibel environment, will be very impatient and irritated. In order to maintain the physical and psychological health and the living environment of people, noise reduction is imperative.
The noises generated in the running process of the centrifugal water chilling unit are substantially composed of three parts: firstly, mechanical noises generated in a meshing process of transmission parts of a centrifugal compressor in the unit; secondly, electromagnetic noises generated in the running process of a motor driving the unit to operate and noises generated by an oil pump supplying oil to a compressor bearing; and thirdly, airflow noises generated by an airflow in a compressor air suction pipeline, an internal flow passage and an exhaust diffuser pipeline.
The mechanical noises generated by meshing of the transmission parts inside the centrifugal compressor are generally reduced by using single methods for thickening the wall of a gear box and improving the machining precision of a gear, the noise reduction methods are relatively single, and the effects are limited.